1. Field of the Invention
The present invention relates to a method of fabricating composite piezo-electric members and a mask used for the fabrication of the same, and particularly to a method of fabricating composite piezo-electric members based on the exposure of synchrotron radiation (SR) X-rays, development and lithography, and to a mask used for the exposure of synchrotron radiation X-rays during the fabrication of composite piezo-electric members.
2. Description of the Related Art
There is known the LIGA (Lithographie Galvanoforming Abformung) process developed in the Karlsruhe Nuclear Research Center in Germany as a micro-fabrication technology for accomplishing three-dimensional micro-structures having the thickness, besides the method based on the anisotropic etching of silicon.
The LIGA process is advantageous in that it can fabricate structures having such a large aspect ratio of several micrometers in width and several hundreds micrometers in thickness based on a unified lithographic treatment, it provides a smooth side surface of the fabricated structure, and it allows a wide choice of material including metals and resins.
Basically, as shown in FIG. 1, an X-ray mask (shown by 2) of a metallic film is made based on electron beam drawing in accordance with a mask pattern (shown by 1) designed by means of a CAD system. A PMMA resist material is exposed to the synchrotron radiation X-rays through the X-ray mask, and next it is rendered the development process, thereby forming a resist structure (shown by 3). Next, metal is deposited thickly in the recessed sections of the resist structure based on plating such as electrocasting, and the resist is removed, thereby forming a metallic structure, i.e., metallic mold (shown by 4).
For the small-scale production, the metallic mold is used directly for forming a final product (shown by 7). For the large-scale production, the metallic mold is used to form plastic molds (shown by 5), and the plastic molds are used to form metallic molds (shown by 6) to form final products (shown by 7).
Accordingly, the LIGA process enables the formation of a large number of products from a mold which is formed by a single exposure of synchrotron radiation X-rays.
The X-ray mask used for the LIGA process needs to be made from a thick metallic film due to a longer exposure time as compared with the X-ray lithography used in semiconductor fabrication. Specifically, metallic films used for the X-ray mask include an Au absorber (KfK) at a 15-.mu.m pressure on a titanium foil of 2-.mu.m thickness, or an Au absorber of a 5-.mu.m thickness formed by electron beam drawing on a silicon thick film.
In making an X-ray mask, the pattern design based on the CAD system or the like for designing arbitrary mask patterns is required (shown by 1 in FIG. 1). In manufacturing an X-ray mask that is durable against the synchrotron radiation X-rays, the electron beam drawing equipment or CVD equipment is required.
These X-ray mask manufacturing facilities are expensive, and even if the X-ray mask is ordered from an external firm, each piece of mask will be considerably expensive.